1. Field of the Invention:
The invention relates to cooking utensils of lightweight and hence of low thermal mass.
2. Description of the Prior Art:
The principal materials used for cooking utensils today are medium-weight aluminum, cast iron, enamelware, glass, heat-proof glass-ceramic and stainless steel. The medium-weight aluminum utensils are the most popular because they heat evenly and quickly. The cast iron utensil if heated slowly will give satisfactory results. The enamelware utensil should only be used on low or medium heat because under certain conditions the enamel finish may tend to soften. Glass utensils also should be used only on warm, low or medium heat settings because the utensils may break with sudden temperature changes. Glass manufacturers recommend a wire grid when using glass on electric surface units. The heatproof glass-ceramic utensils distribute heat slowly and cool slowly so that only the lower heats are recommended. The stainless steel utensils are usually combined with copper, aluminum or other metals for improved heat distribution, but again they work best if used at a medium heat.
One disadvantage with cooking utensils is that in time the bottom wall tends to become warped due to uneven temperature distribution. In the United States, the most common type of electrical surface heating means is the metal sheathed electrical resistance heating element of coiled configuration. These sheathed type heaters have at best a small contact area with the utensil bottom wall, even when both the surface unit and the utensil bottom wall are reasonably flat. The surface unit coils may also become warped due to the high temperatures and the many years they are kept in service. Hence, they may become poor performers even with a utensil with a flat bottom wall.
To offset these possibilities of poor thermal coupling between the sheathed type surface unit and a cooking utensil, the surface units are operated at very high temperatures, up to about 1600.degree.F., at wattages that may approach 3000 watts. This high temperature high energy surface cooking system of today has been deemed necessary (1) to make cooking possible in a utensil which has a very poor thermal coupling with the surface heating unit, and (2) the sheathed type heaters have a small contact area with the utensil bottom wall. Hence, the heater temperature is brought up to temperatures as high as 1600.degree.F in order to bring food temperatures to a temperature only between 212.degree.F and about 450.degree.F. At about 450.degree.F meat starts to char badly, and all frying operations may be performed at temperatures below about 450.degree.F.
The principal object of the present invention is to provide a low thermal mass cooking utensil with a flexible bottom wall that will have optimum thermal coupling capability with a surface heating means so as to enable the use of low energy surface heating means.
A further object of the present invention is to provide a cooking utensil of the class described with a high temperature flexible plastic bottom wall which is capable of conforming to the top surface of a surface heating means to obtain optimum thermal coupling.
A further object of the present invention is to provide a low thermal mass cooking utensil so as to permit the use of a low energy surface heating means and obtain a high thermal efficiency based upon the heat output of the surface heating means and the resulting heat input into the food placed in the cooking utensil.